Still having a nightmare with sump, please help!

[zozo]

The surging is caused by a capacity issue and a single pipe that actually is submerged at both ends. At the top the water is overflowing into it and at the bottom, this pipe stands in a puddle of water. The pipe will fill up entirely from top to bottom and water forced down by its own weight (gravity) and drags in the air with it causing an eddy, a surge with gurgling noises.

When such an air-bubble is in the pipe it actually counteracts gravity, it wants to float and rise to the top to escape. But it can't it is dragged down encapsulated in the water flow. Thus these forces are working against each other making the air-bubble dance up and down in the pipe slowly going further down or stay put dancing, till the weight above it as enough to make it shoot out.

This effect creates an erratic flow speed in the pipe. The water flow slows down by the dancing air-bubble(s) and speeds up the moment the bubble shoots through. It will make a bubbling noise in the sump and the sudden Waterflow acceleration in the pipe and at the top, it sucks in a new bubble making a gurgling noise.

I can imagine it is difficult to imagine or depict this happening from a description... But you could observe this rather natural effect happening if you would make it with transparent tubing. 🙂 I once did and discovered to the origin of the problem by seeing it happen.

It also can happen in an erratic pattern, no issues for days or even weeks and then suddenly start again... Water in pipes dragged down by gravity doesn't have a constant. Sucked in air bubbles differ in size and amount and at one point there will be a threshold playing up. Once a fluctuating flow pattern occurs it keeps itself alive.

What you can do to prevent this is actually very simple... 🙂 This is to divide the drain into 2 separate parts, both connected but as an open system so that air can get in somewhere else than from the top only and the pipe will not be filled entirely with water. To explain this I'll make a little diagram to make it a bit more clear.

The open connection allows air to get in and the overflow standpipe will never be filled with water and suck in no air bubbles. (If it still does it means this pipe is still too long and or too small. You should create an open connection as close to the tank possible.) The piece of horizontal pipe is also needed to prevent water from a deep fall into the sump creating a splashing noise. If you still hear water running noise from the open connection then plug this open connection with a piece of filter sponge. This dampens the noise coming out but still allows air in.

And your noise problems are about over. 🙂

 

[Abi Jones]

Thanks for that, it does make sense. When I first asked for help with this issue a few weeks back before I had any dursos other than the very crude one that came with the used tank we actually had a set up similar to the one in your diagram, only the horizontal pipe was a lot shorter and there was no open connection, the pic is of the previous set up. It was gurgling like mad and the first person to reply said, why haven’t you got the drain going straight down into the sump?! So we changed it!
Im not sure I understand the open connection part, should the air be escaping out of the pipe at that point, so the pipes shouldn’t fit properly together?


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[zozo]

🙂 As said before it's a capacity issue, the noises you hear is air sucked in with the water... This can only happen if you want to drain more than the pipe actually can handle. It needs aeration to function... Unfortunately, I can not create an animated example for you to show what actually is happening and what makes the noise. I can only try to describe it the best as possible in my own words. And I know this ain't that easy and it might be an air-castle for you.

What you have now is a pipe that stands in the sump submerged. Therefore the pipe will fill up partially probably more than 70% with water falling into the sump. You have only one point that aerates and that's the overflow in the tank. The volume in the pipe falls down and drags air with it. That's the noise, this creates a bubble in the pipes water volume slowing down the drain capacity because the bubble wants back out at the top but can't. The moment the bubble shoots out at the other end submerged you'll have a noise again. The water speeds up and sucks back a bubble at the top again noise. And this keeps going on and on.

So you need to create a different entrance and exit point for air to get in and or escape. It shouldn't be trapped in the entire pipes water volume. This you can do for example to unscrew the bulkhead from the standpipe in the picture and replace it with some sort of a Funnel. Made from a bigger size socket slided over so the stand pipe is in it and from that socket lead tubing to the sump. Then the pipes will not fill up with water and drain faster. Air that comes in via the overflow escapes via the open funnel.


You should make sure that the tubing to the sump functions as an open gutter can handle the volume, thus make it a tad bigger than the overflow pipe.

In a simple diagram, it looks like this. Red square in your picture.

 

[zozo]

Here is a picture of my overflow I hope it makes it more clear, it's a different type overflow but that doesn't change the fact that it can have the same noise issues if installed incorrectly.


You see the overflow pipe stands in a bigger pipe and this bigger pipe is the gutter to the sump. It's open. And this setup is since this adaptation as quiet as a mouse. 🙂

 

[Abi Jones]

Thank you so much taking the time to explain, I understand it now. I’ll have a go at adapting my set up today and will let you know how it goes


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[Abi Jones]

One more quick question, is the diagonal cut off at the bottom of standpipe important or is it ok to just have the standpipe ending in a straight edge inside the larger pipe?


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[zozo]

One more quick question, is the diagonal cut off at the bottom of standpipe important or is it ok to just have the standpipe ending in a straight edge inside the larger pipe?


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Good observation and question. 🙂 And yes it can be important depending on the situation, where the standpipe ends. And it can also prevent the sound of falling or dripping water. In my case, it is important because of the pipe stands freely in a wider 90° knee on a horizontal surface without the use of any brackets. Obviously, I needed to cut it diagonally, because a straight cut would block the flow.

The other reason I also noticed if a pipe ends in a straight cut hovering above a horizontal surface (let us say the gutter) then the water will fall on it making a constant splashing or dripping or in some cases a peeing noise of water falling in the water below it. Noises like this can get amplified significantly when it needs to get out through an open aerated tube. And you'll hear a constant peeing concert. Then with a diagonal cut, you can make the pipe touch the surface and water it needs flow into more directly without falling and you still have aeration and it's silent.

These can be the little things but key points to take into account to get sump setups to be as quiet as possible. Prevent water from falling and splashing to much and maintain good aeration.

To clarify I refer to the first diagram I posted with the standpipe internal diagonal cut in the open connection goes al the way to the end.


In the second diagram with the straight cut hovering, this could/will make noise from falling water.


The external diagonal cut you see in the picture from my overflow is not that important but creates an easier entrance if taken apart for maintenance. And I could drill a hole to mount the tube to the wall with a screw, without the use of a bracket. 🙂

 

[Abi Jones]

Thanks for the clarification, it’s very much appreciated Off to b@q shortly to try to find some parts, just hope we can find an elbow big enough to create the air gap as I think the down pipe is 40mm.


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[zozo]

Thanks for the clarification, it’s very much appreciated Off to b@q shortly to try to find some parts, just hope we can find an elbow big enough to create the air gap as I think the down pipe is 40mm.


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I'm not sure about the UK, but mainland Europe the PVC pipe in Metric DIN standard is to jump from 40mm to 50mm. 🙂

 

[not called Bob]

is the double sleeve just recreating the small air gap having the downpipes terminate just above the water line?

 

[Rainbow]

Looks like your water level is right at the top of your Durso. This means you have very little room for the piping to take away the water before a syphon develops, sucking the bit of water there away very quickly. If you cannot drill another drain that is a bit smaller to take a full syphon constantly, I suggest a smaller return pump. That way you have constant flow through the Durso without a syphon.

 

[Abi Jones]

I gave up on it, tried everything everyone advised but nothing worked I have a fluval f6 now and it’s super quiet- shame I still have a standpipe taking up loads of space. Think I’ll be looking for a new tank after Xmas!


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[not called Bob]

could just block it off, until such time some one can pop round and assist

 

[zozo]

I gave up on it, tried everything everyone advised but nothing worked I have a fluval f6 now and it’s super quiet- shame I still have a standpipe taking up loads of space. Think I’ll be looking for a new tank after Xmas!


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As said before it's a capacity issue... 🙂 In this case, your pump is too strong... Pump and drain capacity should be in sync...

The easiest way to find out the drains optimal L/h capacity is a simple modification. That is to place a T splitter in the hose with a valve to it. Best is the place the T and valve in the sump as close as possible to the pump.

Thus the valve fully closed, then the pump runs full capacity to the tank. Open the valve a little and some water will run back into the sump and the aquarium will get a bit less, this way you can easily regulate how much water will be pumped to the tank and the turnover can be synced with the drain capacity.

Depending on the type of valve used it can be regulated pretty precise. Start with a little and just keep opening the valve a tad further in small steps each time till the drain is quiet. At this point, you have reached the drains maximum capacity. And that's physics you simply can not stress and it is what it is without a bigger drainpipe.